For the first time in its history, the Senate will require members and their aides to undergo training to prevent sexual harassment, a victory for advocates and people affected by decades of persistent misbehavior in Capitol Hill offices.

The Senate approved a bipartisan resolution late Thursday to require periodic anti-harassment training for senators, aides and interns. The secretary of the Senate will certify that each office has completed the required training during each Congress.

The measure was the Senate's first effort to change its policies in response to allegations of persistent sexual harassment on Capitol Hill. Since the revelation of harassment and abuse allegations against movie producer Harvey Weinstein, multiple news outlets, including the Washington Post, have documented stories of lewd comments, unwanted touching and other examples of sexual misbehavior in the halls of Congress.

"By passing this resolution, we take a step to ensure that all who work for the Senate are able to do their job without feeling unsafe or uncomfortable," Senate Judiciary Committee Chairman Charles E. Grassley (R-Iowa), co-author of the resolution, said in a statement.

"No place of work is immune to the all-too-prevalent scourge of sexual harassment, but we in Congress have a particular duty to set high standards of conduct," he said.

Lawmakers have come under pressure in recent weeks to improve the Hill's workplace culture, particularly for younger women staffers who are the most frequent victims of abuse. Before the passage of Thursday's legislation, sexual harassment training was optional across the legislative branch; it remains voluntary in the House.

More than 1,300 former congressional aides signed an open letter to congressional leaders calling on Congress to implement mandatory training and reform the process for filing complaints. The letter objected to the requirement that victims pursuing recourse undergo counseling and mediation before taking legal action.

"We believe that Congress's policies for preventing sexual harassment and adjudicating complaints of harassment are inadequate and need reform," the letter from former staffers stated.

Changing the way complaints are filed and addressed will be harder than requiring anti-harassment training. The law establishing the dispute-resolution process for workplace complaints on Capitol Hill was passed in 1995 and has not substantially changed since then. Several bills are in the works to make the process more victim-friendly.

"Making harassment training mandatory in the Senate sends a clear message: harassment of any kind is not and will not be tolerated in Congress," Sen. Amy Klobuchar (D-Minn.), ranking member of the Senate Rules Committee, said in a statement after the chamber approved mandatory training.

An earlier version of the legislation created a survey designed to periodically measure the scope of sexual harassment in the upper chamber. This language was not approved as part of the final resolution, though a Senate aide said leaders of the Rules Committee intend to make sure a survey is carried out.

Training must be completed by each Senate employee covered by the legislation within 60 days and repeated at least as often as each congressional session.

The Washington Post is examining workplace violations on Capitol Hill and the process for reporting them. To contact a reporter, please email elise.viebeck@washpost.com, kimberly.kindy@washpost.com or michelle.lee@washpost.com.